1. Field of the Invention
The present invention relates to a method of and system for, when a fault occurs on a distribution system in a power distribution system, disconnecting only a faulty distribution line section from the distribution line.
2. Description of the Related Art
In general, a power distribution system comprises a distribution substation, a distribution line extended from the substation, and a plurality of section switches for dividing the line into a plurality of line sections. In such a power distribution system, it is required to detect a line section on which a fault has occurred and disconnect the faulty line from normal line sections promptly.
To meet such a requirement, various methods and systems have been proposed and put into practice. Heretofore, a typical system includes a main controller installed in the substation, section controllers installed in individual section switches, and a transmission system for connecting the main controller and each section controller.
If a fault, such as a ground fault, occurs in the n-th section of the distribution line, a fault detecting relay in the substation is activated to open a circuit breaker in the substation. All of the section switches are subsequently no-voltage opened, and the circuit breaker is then reclosed. Thereby, the section (first section) from the substation to the first section switch is supplied with electric power. After reclosing of the circuit breaker, the first section switch, counting from the substation, is closed when its section controller decides that a line section on the substation side (substation side station) are normal. The same operation is repeated up to the n-th section switch.
However, when the substation-side section (load-side section) of the n-th section switch is a faulty section, if the section switch corresponding to the faulty section is closed, the fault detection relay of the station is operated and the circuit breaker is tripped once again. By this breaking operation, the section controller of the n-th section switch determines that the n+1-th section is a faulty section. When the circuit breaker is closed once again, the section switches, up to the n+1-th section switch, are successively closed, and electric power is supplied to the sections just before the faulty section. Thus, power is stopped only in the faulty section.
With such a method, power supply will be cut off in the whole power distribution system. After the power supply to the whole power distribution system is stopped temporarily, the sections are sequentially searched for a fault, beginning with the section closest to the substation. This requires a lot of time.